Newborns start adapting to life outside the womb quickly, with at least some forms of learning possible even while they're asleep, researchers say.

Action Points

Explain that in a classical conditioning experiment, newborns appeared to learn while asleep -- squeezing their eyes shut in response to a tone that predicted a puff of air to their eye.

Explain that this finding does not imply that more elaborate learning such as language also occurs during sleep.

Newborns start adapting to life outside the womb quickly, with at least some forms of learning possible even while they're asleep, researchers say.

Those exposed to a tone followed by a puff of air on their eyelids during sleep rapidly learned to squeeze their eyes tighter after hearing the sound, William P. Fifer, PhD, of Columbia University, and colleagues reported online in the Proceedings of the National Academy of Sciences.

"For babies, learning isn't confined to the awake state," Fifer told MedPage Today. He said studies have shown that sleep is important in shaping and consolidating memories, but "it hadn't been demonstrated that learning could be accomplished during sleep."

"We think this may be important for babies' survival [in terms of] challenges that can occur while they're asleep," he said, such as changes in temperature or oxygen level. In their paper, Fifer and colleagues said the research may be beneficial in understanding the mechanisms behind sudden infant death syndrome, or SIDS, because so-called arousal deficits are a major focus of research.

For their study, the researchers assessed 34 healthy infants between 10 and 73 hours after their birth, who were randomized to an experimental group or a control group.

The newborns were outfitted with cardiorespiratory sensors and a high-density electroencephalographic (EEG) net, then placed in the supine position in a bassinet.

They were fed right before testing in order to "increase the likelihood they would sleep through the entire procedure."

Researchers measured bioelectrical activity in the brain as a tone was played via speakers near the infants' ears, then followed by a puff of air to the right eye. For controls, the tone and the puff of air were initiated randomly.

They also assessed eye movement responses to the air puff. Usable data on these movements were available for 30 newborns.

Fifer and colleagues found that sleeping newborns rapidly learned the predictive relationship between the tone and the puff and showed classical Pavlovian responses when later exposed to the tone.

By the end of the study, those in the experimental group had a four-fold increased likelihood of the "conditioned eye movement response," which entailed squeezing their eyes a bit tighter in preparation for the air as they remained asleep.

Those in the control group didn't have any changes in eye movement after hearing the tone.

The average latency of eye movements decreased from 1,030 milliseconds in the first block of the session to 870 milliseconds in the final block, "becoming significantly closer to the expected puff onset at 900 milliseconds," the researchers wrote.

Newborns also exhibited a positive EEG slow wave, which may reflect memory updating. But the researchers cautioned that this can't be determined conclusively because of the small amount of usable data on this measurement in the control group.

"A baby's brain is capable of learning something about his or her environment and changing their responses because of that environmental stimulus," Fifer said.

Fifer told MedPage Today that it may be useful to replicate the study in adults, since conventional wisdom holds that adults don't learn in their sleep.

"There's no convincing data showing adults can learn while asleep," Fifer said. "That isn't to say it can't be done; there just hasn't been good data."

Fifer cautioned that the learning measured in their study "isn't the kind of learning that has to do with exposure to [or interaction with] some event," such as learning a new language.

Various recorded programs billed as helping babies and toddlers learn while sleeping have been marketed over the years to parents, but scientific studies have generally found they don't work.

The type of learning identified in the current study is more of a conditioned response, Fifer suggested.

"We think this type of learning is a reflex that can be shaped by some change in the environment, just like sucking is a reflex every baby has," he said. "Even that reflex is shaped by the baby's experience with different modes of feeding, whether it's breast-feeding or bottle-feeding or the kind of fluid."

He said the research and the methods may apply to assessment of brain function that could help identify infants at risk of neurodevelopmental disorders ranging from autism to dyslexia.

"It [involves] the same brain circuits implied to be abnormal in some of these disorders," Fifer said. "This could help us in understanding some of the early patterns of brain activity and maturation that may be relevant for those disorders."

The study was supported by the Sackler Institute of Developmental Psychobiology at Columbia University and grants from the National Institutes of Health.

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